Power machine manufacturers produce a number of vehicles with hydrostatic drive systems powered by an internal combustion engine, including skid steer loaders, track loaders, excavators, and utility vehicles. Some machines, such as skid steer loaders, have traditionally controlled drive pumps by stroking the pumps directly via linkages from control inputs such as steering levers without any sort of input or control of engine speed, other than with a manual throttle that is used to set engine speed and is independent of any drive control mechanism.
It has long been known that in certain high load conditions, such as digging, carrying heavy loads over uneven terrain or towing can result in an excessively high load on the engine, causing the engine to bog down. If the load is not reduced, the engine will stop. In machines such as skid steer loaders, an experienced operator would compensate by reducing the input on the hydrostatic drive pumps by de-stroking the travel control input devices. While this approach does work to reduce loads, even the most experienced operators cannot employ this technique to operate machines at peak efficiency.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.